Non-corrosive hydraulic fluids



3,098,825 NON-CORROSIVE HYDRAULIC FLUIDS Richard W. Shifiler, Pittsburgh, Pa., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed July 28, 1958, Ser. No. 751,145 9 Claims. (Cl. 252-78) This invention relates to fluid compositions, and particularly to alkaline inhibited hydraulic fluids which effectively prevent corrosion and staining of non-ferrous metals and which have the advantage of remaining essentially free of precipitation in hydraulic systems adapted for the transfer of mechanical energy. More particularly the invention relates to new and improved alkaline inhibited hydraulic fluids comprising alcohols, alcohol ethers, mixtures of alcohols and ethers, and silicon compounds which contain the CSi bond.

A wide variety of hydraulic fluid compositions have been suggested for use in mechanisms adapted for the transfer of mechanical energy, typical of :which are hydraulic brake systems, recoil devices, shock absorbers, and the like. Among the various hydraulic fluids which are already known in the art are the so-called alkaline inhibited compositions which comprise alcohols, alcohol ethers, or mixtures of both, and an alkaline corrosion inhibitor such as sodium borate, potassium borate or sodium hydroxide, etc. Although hydraulic fluids of this type possess one or more desired characteristics of viscosity-temperature variation, volatility or pour point,

their use has been handicapped to a large extent by the fact that a Wide range of suitable properties cannot be obtained. -F or example, alkaline inhibitor materials have been employed in hydraulic fluids for preventing corrosion of ferrous metals in hydraulic systems. While fluids of this type may be suitable for use in hydraulic systems embodying ferrous metals, such hydraulic fluids, however, are frequently corrosive to aluminum as well as other non-ferrous metals such as brass and copper.

With aluminum, for example, the alkaline inhibitors are believed responsible for producing aluminum stain, apparently aluminum oxide produced by the action of aqueous alkaline solutions, which iscause for rejection when the fluid is tested according to Federal Specification VVF45 la Corrosion Test.

As used herein, the term alkaline inhibited hydraulic fluids refers to fluids comprising one or more compounds from thefclass of alcohols, alcohol ethers, mixtures of such alcolipls and ethers, together with an alkaline inhibitor material in an amount sufiicient to create a pH value of from about 7.0 to 11.5 in the formulated fluids.

In accordance with this invention it has been found that small amounts of silicon compounds which possess the CSi bond are effective corrosion inhibitors when used in admixture with alkaline inhibited fluids. Numerous compounds are operative within the broader scope of the invention including, for example, CSi bonded silanols, silicates, and salt compounds. When blended with alkaline inhibited hydraulic fluids, the defined silicon compounds provide hydraulic compositions which eifectively inhibit corrosion and discoloration of non-ferrous metals such as aluminum, brass and copper, and, in addition, show good stability with substantially no tendency to form precipitates for extended periods of time during storage and use.

United States Patent The silicon compounds used in accordance with the invention are represented by the formula:

)b I l R )d 1 R,,S1 0-8: -a:

(c R), L 1'1, n wherein n represents a value of 0 to 5 R is a monovalent hydrocarbon radical; R can be a hydrogen, aryl, or alkyl group containing from about 1 to 18 carbon atoms or a cation selected [from the group consisting of sodium, potassium and ammonium; and x is a member selected fromthe group of R and OR. In the formula, a represents a value of l, 2 or '3; b and 0 represent a value of 0, l or 2; d represents a value of 0 or 1, and e represents a value of 1 or 2. The silicon compounds contemplated within the scope of the formula possess at least one carbon atom bonded to eachv silicon atom with at least one OR group per molecule. The preferred compounds contain up to about .13 0 carbon atoms to the molecule. Examples of alkyl and aryl groups represented by R are branched and straight chain alkyl groups such as methyl, ethyl, propyl, butyl, amyl, octyl, decyl, undecyl, dodecyl, Z-ethylbutyl, Q-methylpenty-l, Z-ethylhexyl, etc., and substituted or unsubstituted aryl groups such as tolyl, phenyl and cresyl, etc. The monovalent' hydrocarbon radicals represented by R include aliphatic and aryl groups, as above described, as Well as carbalkoxyalkyl groups, such as carbethoxyethyl, wherein the al-koxy and alkyl groups, each, may contain from about 1 to 18 carbon atoms. The groups represented by R and R may be alike or diiferent.

Preferred silanol compounds encompassed within the scope of the above formula include triphenylsilanol and the silanediols such as dipheny-l silanediol, dimethyl silane diol, diethyl silanediol, methylphenyl silanediol, tetramethyl disiloxanediol-1,3 and other silancdiols which contain aryl and/or alkyl substituents occupying the 1, 2, or 3 positions on each silicon atomwith the remaining valences being satisfied with hydroxyl groups. The substituent group may consist of methyl, ethyl, propyl, butyl, octyl, decyl, tolyl, phenyl, cresyl, or a carbalkoxy-substituted hydrocarbon group.

For silicate compounds (falling within the scope of the above formula the trialkoxy or triaryloxy compounds are preferred. Examples of such compounds include methyl triethoxysilane, ethyl triethoxysilane, dimethyl tetra-2- ethylhexoxy disiloxane, phenyl triethoxysilane, methyl triphenoxysilane, beta-carbethoxyethyl triethoxysilane, as Well as other CSi bonded silicates which contain substituent groups occupying the l, 2 or 3 positions on each silicon atom, as above described, with the remaining valences being occupied by ester groups.

The preferred CSi bonded silicon salt compounds are the mono-, di-, or trisodium, potassium or ammonium salts of methyl, ethyl, propyl, butyl, amyl, phenyl, cresyl, etc., siloxanes.

The above CSi bonded silanols, silicates and salt compounds can be used alone or in combination for the.

purposes described herein. Each. group of silicon compounds constitutes a well known class of prior art materials.

Preferred compositions prepared in accordance with this invention are the alkaline inhibited hydraulic fluids which contain one or more compounds from the class of alcohols, alcohol ethers, mixtures of such alcohols and Weight percent Lubricant 15 to 35 Dilucnt 65 to 85 Antioxidant to 2 Alkaline inhibitor 0.1 to 2 Silicon compound 0.0001 to 1.0

The lubricant portion contains one or more polyhydric alcohols or polyhydric alco'hol ethers including polyethers, or a mixture of polyhydric alcohols and ethers, all preferably having average molecular weights of at least 300 as a minimum. The lubricant can also contain, as modifiers, esters and polyesters of polyhydric alcohols; reaction products of alkylene oxides and polyfunctional amines, e.g., polyalkylene .polyamines; ethanolarnines and the like; castor oil; blown castor oil, i.e., castor oil which is polymerized by air oxidation; bodied castor oil, i.e., castor oil which is polymerized by heat alone; acetylated oastor oil; glycol modified castor oil, and the like, or mixtures thereof. The diluent portion acts as a solvent permitting adjustments to the composition viscosity, as desired, and can comprise one or more monohydric alcohols or dihydric alcohol monoethers or mixtures thereof and can contain from 0 to 50 weight percent dihydric alcohols all of which have average molecular weights below about 300.

Any suitable method can be used in preparing our hydraulic liquid compositions. The components can be added together or one at a time in any desired sequence. It is preferable, however, to add the antioxidant and alkaline inhibitor as a solution in the alcohol component. It is also preferable to warm this solution during its preparation in order to facilitate dissolution. All components are mixed until a single phase composition is obtained.

Representative of polyhydric alcohols which can be used in the fluid compositions are the alkylene glycols, ie.g., ethylene glycol, propylene glycol, the bntanediols, the pentanediols, the hexanediols and the like, the polyoxyalkylene glycols such as polyoxyethylene glycols, polyoxypropylene glycols, polyoxybutylene glycols and the like, mixed polyoxyalkylene glycols, e.g., polyoxythylenepolyoxypropylene glycols, and polyoxyalkylene triols. Representative ofpolhydric alcohol ethers are the alkyl and aryl monoethers, diethers and triethers of polyhydric alcohols such as those specified above. Examples of polyhydric alcohol ethers are ethylene glycol monomethyl ether, dipropylene glycol monoethyl ether, polyoxyethylene glycol monophenyl ether and the like, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, polyoxypropylene glycol dibutyl ether and the like.

The useful antioxidants and alkaline inhibitorsare well known materials. Typical antioxidants include phenolic compounds, such as 2,2-di-(4-hydroxyphenyl)propane and polymerized trimethyldihydroquinoline and the like, aminessuch as phenyl alpha-naphthylarnine and .phenyl beta-naphthylamine, and the like, as well as hindered phenols and the like. Alkaline inhibitor materials which can be employed in an amount sufficient to maintain alkaline conditions in the fluid composition, i.e. a pH value of from about 7.0 to 11.5, include alkali metal hydroxides, e.g. potassium hydroxide, sodium hydroxide,

etc.; alkali metal borates, e.g. sodium borate, potassium.

nitrites; amines such as morpholine, ethanolamine, triethanolamine, etc.; amine salts such as, for example, the monoor dibutyl ammonium bora-tes and phosphates.

Organic orthosilicate, i.e., organo-si-licon compounds characterized by only alkoxy or only aryloxygroups attached to a single silicon atom or to groups of silicon atoms interconnected by silicon to oxygen to silicon bonds, have been used heretofore in heat transfer fluids and their use as inhibitors in brake fluids is described in copending application, Serial Number 633,178, filed January 9, 1957, now abandoned. Freshly prepared hydraulic fluids thus inhibited show a beneficial effect with respect to metal staining as well as a lack of precipitation in corrosion tests at 212 F. and in Federal Specification VVF-45 1a Water Tolerance Tests at 140 F. However, organic orthosilicates such as ethyl silicate eventually precipitate due to small amounts of water inevitably present in any hydraulic system which hydrolyze the silicate to insoluble silica or condensed silica polymers. Additionally, orthosili'cate-inhibited fluids after being stored for extended periods of time, especially in tin-lined containers, such as those ordinarily used to package fluids, are subject to failure in the Water Tolerance Test due to metal contaminants, soldered seams, etc, which have a pronounced effect in promoting and accelerating the rate and degree of precipitation. However, with alkaline inhibited fluids containing the CSi bonded silicon compounds described herein, the hydraulic fluids remain essentially free of precipitation overextended periods of time by virtue of such compounds being substantially resistant to hydrolysis and polymerization. Although there is some opportunity for C--Si bonded silicon compounds to hydrolyze and polymerize, the substituent groups apparently act as hindering groups which retard the rate of hydrolysis and polymerization, or as solubilizing groups in the event that polymerization occurs. As an example, diphenylsilanediol possesses only two reactive groups, as opposed to the four reactive substituent groups on ethyl silicate through which polymerization can proceed. In this respect the CSi bonded silicon corrosion inhibitors defined herein differ widely from the organic orthosilicates.

The following examples illustrate the fluid compositions of the invention and are not to be considered as limiting the scope of the invention.

EXAMPLE 1 Ethylene glycol monobutyl ether 33.75 Diethylene glycol mo-noethyl ether 25.49 Ethylene glycol 8.26

To parts by weight of this base fluid mixture, 0.5 part by weight of 2,2-di-(4-hydroxyphenyl)pro1:1ane as antioxidant and 0.5 part by weight of borax, i.e., sodium tetraborate (Na B O -5H O), as alkaline inhibitor were added. In the above base fluid and those hereinafter, the antioxidant and alkaline inhibitors were first dissolved at a temperature of 70 C. to 100 C. in the ethylene glycol and the resulting solution was then introduced into the remainder of the mixture.

EXAMPLE 2 To 100 parts by weight of the alkaline inhibited mixture of the fluids prepared in Example 1, eight hydraulic liquid compositions were formulated which contained the fol lowing CSi bonded silicon inhibitors.

The above hydraulic compositions thus prepared were tested for corrosion by incorporating in each of the liquid composition-s five parts by volume of water. 'Six strips, one each of the following (bolted together in the order listed), tin, steel, aluminum, cast iron, brass and copper, were immersed in each of the hydraulic liquid-water solutions and the temperature of the solutions raised to 212 F. This temperature was maintained for five days. At the end of this period all of the test strips remained clean and bright without any corrosion or staining. Without the silicon compounds each of the fluid compositions caused corrosion and staining of the test strips.

EXAMPLE 3 An alkaline inhibited base fluid containing the following materials was prepared. Polyoxyethylene-polyoxypropylene glycol monobutyl ether (2000 S.U.S. at 25 C.)

parts by volume 12.5 Polyoxyethylene-polyoxypropylene glycol monobutyl ether-(260 S.U.S. at 25 C.) do 12.5 Diethylene glycol monoethyl ether do 60.0 Diethylene glycol monobutyl ether do 10.0 Ethylene glycol do 5.0 2,2adi-'(4-hydroxyphenyl) propane percent by wt 0.5 Sodium tetrabOPate-SH O do 0.5

To 100 parts by weight of the alkaline inhibited mixture of the fluid prepared in Example 3, two hydraulic fluid compositions were formulated, one of which contained .005 part by Weight of diphenylsilanediol and the other .005 part by weight of methyl triethoxysilane. The hydraulic fluid compositions were prepared for corrosion testing by incorporating therein five parts by volume of water and each were tested for corrosion with metal strips as indicated above in Example 2. The CSi bonded silicon inhibitors substantially eliminated corrosion and staining of all the test strips whereas without the added silicon compound each fluid caused corrosion and staining of the metals.

EXAMPLE 4 An alkaline inhibited base fluid containing the following materials was prepared. Polyoxyethylene-polyoxypropylene glycol monobutyl ether (260 S.U.S. at 26 C.)

parts by volume Diethylene glycol m'onomethyl ether do Ethylene glycol monobutyl ether do 25 Ethylene glycol monoethyl ether ..do 25 Ethylene glycol do 5 2,2-di-(4 hydroxyphenyl)propane percent by -wt 0.5 Sodium tetraborate-d0H O do 0.5

6 EXAMPLE 5 An alkaline inhibited base fluid containing the following materials was prepared. Polyoxyethylene-polyoxypropylene glycol monobutyl ether (260 S.U.S. at 25 C.)

parts by volume 25 Diethylene glycol monoethyl ether do 61 'Polyoxypropylene glycol (150 avg. mol. wt.) do 5 Ethylene lglycol do 4 Reaction product of about equal parts by weight of castor oil and polyoxypropylene glycol (150 avg. mol. wt.) do 5 2,2-di-(4-hydroxyphenyl)propane percent by wt 0.5 Potassium tetraborate do 0.5

To 100 parts by weight of the alkaline inhibited mixture of fluids of Example 5, five hydraulic liquid compositions were formulated which contained 0.005 part by weight of beta-carbethoxyethyl triethoxysilane, 0.005 part by weight of diphenylsilanediol, 0.005 part by weight of phenyl tm'ethoxysilane, 0.01 part by weight of methyl triethoxysilane, and 0.005 part by weight of amyl triethoxysilane, respectively.

With each fluid composition thus formulated the CSi bonded silicon inhibitors eliminated the corrosion and staining of all the test strips when such fluids were subjected to the corrosion test described in Example 2. Without the added silicon inhibitors each hydraulic fluid caused corrosion and staining of the test metals.

EXAMPLE 6 Table I below illustrates a direct comparison between 1 the hydrolytic stability of alkaline inhibited hydraulic fluids containing organic orthosilicates and the CSi bonded silicon inhibitors of the invention. The coma temperature of 140:3 F. and held at that temperature to the point of failure. Failure of the test occurs when the hydraulic fluids show precipitation, separation, sedimentation, or crystallization. This test demonstrates the relative resistance of the organic orthosilicate and the CSi bonded silicon-containing fluids of this invention to hydrolysis and polymerization which results in precipitation.

Without the added silicon inhibitors each Table l EXTENDED WATER TOLERANCE TEST (3%% ADDED WATER) AT F. WITH INHIBITED BRAKE FLUIDS Days to failure due to precipitation 1 Inhibitors Base Base fluid of fluid of Ex. 3 Ex. 4

None (control 28+ 28+ Organic orthosilicates:

0.003% ethyl si1icate 2 3 0.006% ethyl silicate 1 1 0.005% hexa-2-ethylbutoxydisiloxane 4 28+ 0.01% hexa-2-ethylbutoxydisiloxane 3 4 CSi bonded silicates:

0.005% Methyl triethoxysilane 28+ 28+ 0.01% Methyl triethoxysilane 28+ 28+ 0.005% Amyl triethoxysilane- 28+ 23+ 0.01% amyl triethoxysilane 28+ 28+ 0.005% phenyl triethoxysilane. 28+ 0.01% phenyl tricthoxysilane 28+ 0.01% dimethyl tetra-2-ethylhexoxydisiloxane.. 28+ 28+ 0.02% dimethyl tetra-Z-ethylhcxoxydisiloxanen 28+ 28+ 0.005% beta-carbethoxyethyl triethoxysilane 28+ 28+ 0.01% beta-carbethoxyethyl triethoxysilanc.. 28+ 28+ CSi bonded silanols:

0.005% dlphenysilanediol 28+ 28+ 0.01% diphenylsilanediol 28+ 28+ 0.005% triphenylsilanol 28+ 28+ 0.01% triphenylsilanol 28+ 28+ 0.005% tetramethyl disiloxanediol-1,3 28+ 28+ CSi bonded salts: 0.00156% sodium salt of methyl siloxane 28+ 28+ 0.00312% sodium salt of methyl siloxane 28+ 28+ 1 sign indicates that failure has not occurred.

7 EXAMPLE 7 Table II below illustrates the superior stability of CSi bonded silicon com-pounds in alkaline inhibited hydraulic fluids which are stored in tin-lined containers over extended periods of time. As little as 7 ppm. of combined tin and lead contamination in organic orthosilicate-inhibited hydraulic fluids has been found to promote copious precipitates in Water Tolerance and Corrosion Tests. In Table II below, each of the formulations were stored in tin-lined containers for several days at an elevated temperature prior to performing the Water Tolerance Test at 140 F. as described in. Federal Specification VV-F- 451a (Sec. 3.7.2). This test is the same as described in Example 6 except that the test period is 24 hours. Under these conditions the fluids containing organic orthosilicates; i.e., ethylsilicate or hexa-2-ethylbutoxydisiloxane formed heavy precipitates. The fluids containing the CSi bonded silicon inhibitors were free of precipitates.

radicals having 1-18 carbon atoms, aryl radicals having 6-18 carbon atoms and cations selected from the group consisting of sodium, potassium and ammonium; x is a member selected from the group consisting of R and OR; a represents a value of 1 to 3', b and c represent a value of 0 to 2; d represents a value of 0 to 1; and 2 represents a value of 1 to 2, said silicon compound being present in an amount sufficient to eifectively inhibit corrosion.

2. A non-corrosive hydraulic brake fluid composition consisting essentially of a lubricant selected from the group consisting of polyhydric alcohols and polyhydric alcohol ethers and mixtures thereof, said alcohols and ethers having a minimum average molecular weight of at least 300, and a diluent selected from the group consisting of dihydric alcohols and the manoalkyl ethers of dihydric alcohols, said dihydric alcohols and ethers having average molecular weights of below 300; an alkaline inhibitor suificient to provide a pH value of from about 7.0 to 11.5, and as a corrosion inhibitor, from about Table II WATER TOLERANCE TESTS (3%% ADDED WATER), ONE DAY AT 140 F WITH INHIBITED BRAKE FLUIDS Inhibitors Base fluid of Base fluid of Ex. 4

None (Control) Trace haze Clear. Organic Orthosilicates:

0.003% ethyl silicate. Flocculent precipitate. 0.006% ethyl silicate. Flocculent pre- Flocculent precipitate, 0.005% hexa-Z-ethylbutoxydisiloxane cipitate. slight haze 0.01% hexa-2-ethylbutoxydisiloxane Flocculent precipitate. CSi bonded silicates: 0.005% methyl triethoxysilane Clear Clear.

0.01% methyl trieth0xysilane (1 .Do. 0.005% amyl triethoxysilane Do. 0.01% amyl triethoxysilane Do. 0.005% phenyl triethoxysilan Do. 0.01% phenyl trieth0xysilane D0. 0.01% dimethyl tetra-Z-ethylhexoxy-disi- Do.

soloxane. 0.02% dimethyl tetra-Z-ethylhexoxy-clisi- Do.

oxane. 0.005% beta-carbethoxyethyl triethoxy-sil- V. sl. haze Do.

ane. 0.01% beta-carbethoxyethyl triethoxy-sil- Clear D0.

ane. CSi bonded silanols:

0.005% diphenylsilanediol Slight haze D0. 0.01% diphenylsilanedioh do D0. 0.005% triphenylsilanol. Trace haze Do 0.01%triphenylsilano1 0 Do. 0.005% tetramethyl disilixanediol-l,3 Slight haze Do. CSi bonded salts:

0.00156% sodium salt of methyl siloxane Trace haze Do. 0.00312% sodium salt of methyl siloxane Clear D0.

CSi bonded compounds remained clear after 2 days.

Although the invention has been illustrated by the preceded examples, the invention is not to be construed as limited to the materials employed in the above exemplary examples, but rather, the invention encompasses the generic concept as here-inbefore disclosed. Various modifications and embodiments of this invention can be made without departing from the spirit and scope thereof.

What is claimed is:

1. A non-corrosive hydraulic brake fluid composition consisting essentially of a hydraulic fluid selected from the group consisting of polyhydric alcohols, polyhydric alcohol ethers and mixtures thereof; an alkaline inhibitor sufiicient to provide a pH value of from about 7.0 to 11.5, and as a corrosion inhibitor therefor a CSi bonded silicon compound of the formula (OR')b Riv-Si 0.0001 to 1.0 percent by Weight of a CSi bonded compound of the formula:

0 R) (OR) I all Il -Si I r L e in wherein n represents a value of 0 to 5; R is a radical having 1-18 carbon atoms, selected from the group consisting of alkyl, aryl and carbalkoxyalkyl; R is a member selected from the group consisting of hydrogen, alkyl radicals having 1-18 carbon-atoms, aryl radicals having 618 carbon atoms, and cations selected from the group consisting of sodium, potassium and ammonium; x is a member selected from the group consisting of R and OR; a represents a value of 1 to 3; b and c represent a value of 0 to 2; d represents a value of 0 to 1; and e represents a value of 1 to 2.

3. A non-corrosive hydraulic brake fluid composition consisting essentially of 15 to 35 weight percent of a lubricant selected from the group consisting of polyhydric alcohols, polyhydric alcohol ethers and mixtures thereof, said alcohols and ethers having a minimum average molecular weight of at least 300; from 65 to weight percent of a diluent selected from the group consisting of dihydric alcohols and the monoalkyl ethers of said dihydride alcohols, having average molecular weights of below 300; an alkaline inhibitor sufliciemt to provide a pH value of firom about 7.0 to 11.5 and as a corrosion inhibitor, a C-Si bonded silicon compound of the formula:

b a alias l member selected from the group consisting of R and OR;

a represents a value of 1 to 3; b and 0 represent a.value of 0 to 2; d represents a value of 0 to 1; made re resents a value of 1 to 2, said silicon compound being present in an amount suflicient to, effectively inhibit corrosion.

4. A non-corrosive hydraulic brake fluid composition consisting essentially of 15 to 35 weight percent of a lubricant selected from the group consisting of polyhydric alcohols, polyhydric alcohol ethers and mixtures thereof, said alcohols and others having a minimum average molecular weight of at least 300; from 65 to 85 weight percent of a diluent selected from the group consisting of dihydric alcohols and the monoalkyl ethers of said dihydride alcohols, having average molecular weights of below 300; an alkaline inhibitor sufiicient to provide a pH value of from about 7.0 to 11.5 and as a corrosion inhibitor, from about 0.0001 to 1.0% by weight of a C-Si bonded silicon compound of the formula:

u R'nL in wherein n represents a value of 0 to 5; R is a radical, having 118 carbon atoms, selected from the group consisting of alkyl, aryl, and carbalkoxyalkyl; R is a member selected from the group consisting of hydrogen, alkyl radicals having 1-18 carbon atoms, aryl radicals having 6-18 carbon atoms, and cations selected from the group consisting of sodium, potassium and ammonium; x is a member selected from the group consisting of R and OR; a represents a value of 1 to 3; b and 0 represent a value of 0 to 2; d represents a value 0 to 1; and e represen a value of 1 to 2.

5. The hydraulic brake fluid compositi n 0f 01mm 4 wherein the CSi bonded silicon compcund 1S dlpheflylsilanediol.

The hydraulic brake fluid composition of claim 4 h i th C-Si bonded silicon compound is tetramethyl disiloxanediol.

7. The hydraulic brake fluid composition of claim 4 wherein the CSi bonded silicon compound is methyl triethoxysilane.

8. The hydraulic brake fluid composition of claim 4 wherein the Cfi i bonded silicon compound is betacarbethoxyethyl triethoxysilane.

9. The hydraulic brake fluid composition of claim 4 wherein the C-Si bonded silicon compound is amyl triethoxysilane.

References Cited in the file of this patent UNITED STATES PATENTS 2,345,586 Clark Apr. 4, 1944 2,407,037 Sowa Sept. 3, 1946 2,834,748 Bailey et a1. May 13, 1958 2,905,642 Miller et al Sept. 22, 1959 2,914,548 Sch-roll Nov. 24, 1959 2,995,590 Peeler et a1. Aug. 8, 1961 FOREIGN PATENTS 550,090 Canada Dec. 10, 1957 

1. A NON-CORROSIVE HYDRAULIC BRAKE FLUID COMPOSITION CONSISTING ESSENTIALLY OF A HYDRAULIC FLUID SELECTED FROM THE GROUP CONSISTING OF POLYHYDRIC ALCOHOLS, POLYHYDRIC ALCOHOL ETHERS AND MIXTURES THEREOF; AND ALKALINE INHIBITOR SUFFICIENT TO PROVIDE A PH VALUE OF FROM ABOUT 7.0 TO 11.5, AND AS A CORROSION INHIBITOR THEREFOR A C-SI BONDED SILICON COMPOUND OF THE FORMULA 